SOD is a ubiquitous enzyme present in plants, animals and microbes, which protects them against oxidative damage caused by superoxide radical (hereinafter, referred to O2−). The enzyme dismutates superoxide radical into hydrogen peroxide and oxygen as per the following redox reaction:2O2−−+2H+=H2O2+O2 Thus, SOD has implications in all those reactions, wherein O2−− is produced in the amount leading to cellular injury. According to the U.S. Pat. No. 6,485,950, we have extracted an autoclavable superoxide dismutase from Potentilla that could be autoclaved and shows activity at sub-zero temperature. Due to prevalence of Potentilla at difficult to access location of high altitude, and industrial implications of SOD as mentioned in our U.S. Pat. No. 6,485,950, it was essential to develop a system for the production of SOD of Potentilla in E. coli so as to obtain the SOD when desired.
Below is given state of the art knowledge in relation to isolation of SOD genes from various sources and their expression in E. coli, to produce SOD in recoverable quantities.
Reference may be made to document (1) by Wang, Z., He, Z., Shen, Q., Gu, Y., Li, S, and Yuan, Q. (J. of Chromatography B, 2005. 826: 114-121) wherein Cu/Zn SOD gene from Cordyceps militaris was overexpressed in E. coli. 
Yet another reference may be made to document (2) by Liu, W., Zhu, R. H., Li, G. P., and Wang, D. C. (Protein Expr. Purif. 2002. 25: 379-388) wherein production of high yield of recombinant duck Cu/Zn SOD was achieved in E. coli. 
Reference may be made to yet another document (3) by Pan, S. M., Hwang, G. B., and Liu, H. C. (Bot. Bull. Acad. Sin. 1999. 40: 275-281) wherein over-expression and characterization of cytosolic Cu/Zn SOD from rice in E. coli was achieved.
Reference may be made to document (4) by Hartman, J. R., Geller, T., Yavin, Z., Bartfeld, D., Kanner, D., Aviv, H., and Gorecki, M. (Proc. Natl. Acad. Sci. USA. 1986. 83: 7142-7146) wherein high-level expression of enzymatically active human Cu/Zn SOD was reported in E. coli. 
Reference may be made to document (5) by Ken, C. F., Lin, C. T., Shaw, J. F., and Wu, J. L. (Marine Biotech. 2003. 5: 167-173) wherein the Cu/Zn SOD from zebrafish was over-expressed in E. coli and the active enzyme was purified.
Reference may be made to document (6) by Kim, T. S., Jung, Y., Na, B. K., Kim, K. S., and Chung, P. R. (Infect. Immun. 2000. 68: 3941-3948) wherein the Cu/Zn SOD gene from Faciola hepatica was cloned and expressed in E. coli. 
The drawbacks are:                1. There is no SOD gene that is isolated from Potentilla, a source of Cu/ZnSOD that is autoclavable and functions at sub-zero temperature.        2. There is no SOD gene that is isolated from Potentilla and made to express in E. coli.         3. There is no SOD gene that is made to express in E. coli leading to SOD protein that is shown to be autoclavable.        4. There is no SOD gene that is made to express in E. coli leading to SOD protein that is shown to function at sub-zero temperature.Comparative Data of Present SOD with other Known SOD        
Present inventionPrior artThe maximum thermostability ofThe maximum thermostability of SOD isSOD described so far is at 80° C.37° C. to 50° C.reference from Bueno P., Verla, J.,Gallego, G. G., and Rio del A. L. (PlantPhysiol. 1995. 108: 1151-1160) whereinthe thermostability of Cu/Zn SODisolated from the cotyledon of watermelon has been shown, SOD activityreduced:(a) by 40% after 4 hour of incubation at50.° C.;(b) by 50% after 15 minute of incubationat 70° C.;(c) by 80% after 60 minute of incubationat 80° C.;and(d) by 100% after 15 minute ofincubation at 100° C.Reference may be made to Document byMiyata, K., Maejima, K., and Tomoda, K.(U.S. Pat. No. 4,563,349; Jan.7, 1986) wherein SOD has been reportedfrom a microorganism belonging togenus Serratia having the thermostabilitycharacters as follows: (a) Stable at 37° C.for 60 minutes; Inactivated by 50% whenincubated at 50-60° C. for 60 minutes;and Inactivated by 100% when incubatedat 80° C. for 5 minutes.stability without adding an externalExternal stabilizer is required to enhancestabilizer [the addition of hydrogenthe stability of the product contains thisperoxide trapping agent, polyols, andenzyme.sugars etc. are required to stabilise theReported SODs do not retain theirenzyme from other sources such asactivity at ambient temperature unlessgerminated plant seedsstabilized by the addition of polyols,sugars or any other stabilizing agent(Bresson-Rival; Delphine; Boivin;Patrick; Linden; Guy; Perrier; Erric;Humbert; Gerard; 1999; U.S. Pat. No.Wide range of temperatureTemperature range for SOD activity hasfunctionality from sub-zero to abovebeen reported between 5 to 45. degree. C.50. degree. C. temperature whichHakam, N. and Simon, J. P. 1996.would immensely enhance the utilityPhysiol. Plant. 97: 209-216). However,of the enzyme and its products and bethermostability and lower temperaturesafer for use for humans.for catalyzing dismutation ofO.sub.2.sup.-. are not reported for the sameenzyme.Present enzyme is autoclavable.There is no report for autoclavable SOD.When SOD is to be injected in thebody, a sterile composition would beneeded and for that an autoclavableSOD would be an ideal one.Moreover, in reperfusion applicationsand storage of organs at lowtemperature, an autoclavable SODwould be required which can functionefficiently at low temperature as well.Apart from the use of autoclavedSOD in pharmaceuticals and medicalfields, sterile SOD will also be achoice in the cosmetic and food industry.